Typical examples of heat pump apparatuses are refrigeration cycle apparatuses used in appliances such as air conditioners, refrigerator-freezers, and water heaters. In conventional refrigeration cycle apparatuses, chlorofluorocarbon or alternative fluorocarbon is used as a refrigerant. However, such refrigerants are responsible for environmental problems such as destruction of the ozone layer and global warming. Patent Literature 1 discloses a refrigeration cycle apparatus using water as a refrigerant that places very little load on the global environment. The refrigeration cycle apparatus disclosed in Patent Literature 1 is shown in FIG. 12.
The refrigeration cycle apparatus 100 includes an evaporator 110, a condenser 120, a first circulation path 150, and a second circulation path 160. The upper portion of the evaporator 110 is connected to the upper portion of the condenser 120 by a first communication path 130. Compressors 131 and 132 are provided in the first communication path 130. The lower portion of the evaporator 110 is connected to the lower portion of the condenser 120 by a second communication path 140.
It has also been desired to increase the efficiency of refrigeration cycle apparatuses for the purpose of reducing the load on the global environment. Patent Literature 2 discloses a refrigeration cycle apparatus using an ejector as a means for recovering expansion energy of the refrigerant.